Legato percussion circuit



Dec. 15, 1964 D. R. KERN LEGATO PERCUSSION cRcUIT 2 Sheets-Sheet l Filed Aug. 29, 1962 nlullllll.

INVENTOR.'

Dec. 15, 1964 D. R. KERN 3,161,714

LEGATO PERCUSSION CIRCUIT Filed Aug. 29, 1962 a sheets-sheet 2 I! g F1@ fig ./51 /C{ |X l l l H T /IF IN VENTOR.'

United States Patent Chice 3,liil,714 Patented Dec. 15, 1964 sasrnia LEGAT@ PERUUSSTN CRCUT Donald ik. Kern, (Chicago, lll., assigner te Hammond Organ Company, Chicago, Eil., a corporation of Eelaware Filed Aug. 29, 1962, Ser. No. 220,227 lll Claims. (Cl. 04u-1,26)

This invention relates in general to an arrangement for providing percussion in response to legato or normal operation of the playing keys of an electrical organ and more particularly relates to an arrangement for providing legato percussion without additional manual key contacts such as are ordinarily necessary in providing such percussion.

When it is desired to provide percussion tone signals during staccato passages on the organ, the problems are not so involved since each key is quickly operated and released. Each tone signal can therefore be independently utilized for initiating a percussive tone.

It the organ is to be played in a legato manner, however, substantial problems arise. Thus, the keys are operated for what is a comparatively long period of time and held operated during the operation of other keys. This creates a problem in distinguishing one signal from another for enabling the apparatus to provide separate percussive tones for each operated key. Generally, additional key, contacts are provided under the playing keys to indicate when the respective keys are operated so that the apparatus will provide separate pereussive tones for the successively operated keys. This, of course, is expensive.

It is therefore proposed in the present invention to utilize one switch of a group of switches normally provided for each key to derive respective harmonics for initiating percussion irrespective of the factthat one or more keys are already operated.

lt is therefore a primary object of this invention to provide an improved arrangement for sounding tones percussively in response to a legato style or manner of ,playing the keys in an organ.

The above and other objects of the present invention will become apparent on examination of the following specification and claims together with the drawings wherein: K'

FIG. l illustrates one circuit arrangement for deriving` a signal to control a tone envelope control means in re* sponse to the simultaneous operation of a plurality of keys; and

FlG. 2 illustrates the invention utilized with another type tone envelope control means.

In FTG. 1 of the drawings, a legato percussion signal circuit for use in an organ is indicated generally by the reference character l'. A series of tone generators A-X are indicated at the lower left portion of the drawing, and these are Vconnected via respective resistors 'Ria-Rlx and switches All-X1, when operated by respective playing keys to a common lead 12. Lead l2 extends to ground through a percussion control switch and the primary Pl of a transformer Tl. Each switch Al-Xl is part of a group which is operated by a respective playing key, and the switches ofeach group provide respective tone signals 'over lead i3 to a primary P2 of a transformer T2. The switches Al-Xl would normally provide the 8th harmonic of any fundamental associated with the respective playing kei but since this is a seldom used harmonic, the key contact is utilized for percussion, as well. The lead 12 is also optionally connected by means of a switch llo through a filter indicated by the block 'ld to the primary P2 of a trans- `former T2.

A 17,000 cycle input signal from a source CP is also `connected to lead 12 through a resistor R if the common percussion switch l5 is operated. Therefore, whenever a playing key is operated to close one of the switches Al-Xl, the effective resistance of the keying resistance plus the generator impedance is shunted across the primary Pll of transformer Tll causing the amplitude of the 17,000 c.p.s. signal across primary P1 to drop. As additional keys are played closing their respective contacts A1 to X1, more shunting resistances are placed across the primary P1 resulting in a decrease in the amplitude of the 17,000 c.p.s signal each time another key is played. The 17,000y cycle tone is prevented from being applied to the primary P2 by iilter lid when switch lo is closed and therefore only the signals supplied by tone generators A-X are extended to lead ll from lead l2.

The secondary of transformer Tl feeds the legato percussion signal circuit l0. This circuit comprises a tube 20, whose grid is c'onected to the output of transformer Tl through a capacitor Cl. Connected to the plate of tube Z0 a l0 kc. high pass filter 22 passes the 17,000 cycle signal provided at the transformer Tl together with any change in amplitude therein introduced by operation of the switches Alt-Xl to the grid of a diode 24. The lter 22 rejects the tone signals from generators A7 to (7 applied to transformer Tl as a result of closure of contacts All to X1 from entering signal circuit l0. The diode 2,4 is a detector to rectify the 17,000 cps. signal and produce a positive pulse of l7,000 c.p.s. signal as any switch Al. to Xlr is closed. This pulse is then amplified by triode 2e and connected to a l0 kc. low pass iilter 28 which removes the l7,000 c.p.s, signal completely, leaving only the negative pulse envelope each time any switch All to Xl is closed.

This negative pulse is then applied to a three stage amplifier comprised of triodes 250, 32, and 3d. The positive pulse appearing at the plate of triode 34 can be used to operate many control devices for providing percussion.

Thus, the plate circuit of tube 34 is connected to B+ through a resistor Rb and a bypass circuit comprising a capacitor C9 and coil L6 is provided to remove any 17,000 c. p.s. signal that may leak through. A capacitor Cllil connects the output of tube 3d to the grid of a signal tube 36. The grid of tube 36 is biased by a --30 volt source through a resistor Rc and its cathode is connected to ground so that the tube 36 is normally non-conductive.

The plate of tube 3io is connected to a B+ source through a relay 3S having a capacitor CE1 in shunt therewith. Thus the grid of tube 36 must rst be driven in a positive direction and when tube 3d begins to conduct, the capacitor Clit provides a time delay to insure .the relay 33 operates for a desired time interval` If desired, the percussion control switch l5 may be located in series with relay 30 instead of as shown.

The .relay 30 has a pair of make contacts (t0 adapted to place Va +30 volt potential across a voltage divider comprising resistors` Rd, Re and Rf. A switch 42 enables resistor Re to be shunted by a comparatively low value resistor Rg. A tap d4 between resistors Rd and Re is connected as indicated to a center tap on the secondary of transformer TZ and through a capacitor C12 to the cathodes of a pair of push pull amplifiers do and'li which are in turn connected to a source of +37 Volts.

`The grids of tubes i4 and i6 are connected at opposite ends of the secondary of transformer T2 for amplifying the tone signals suppliedto the primary P2. The plates of Vtubes 46 and 48 are connected through respective ends of a transformer primary P3 to B+, and this transformer Yfeeds an youtput amplier AM and loud speaker S.

The tubes i6 and du are thus arranged as in a standard control tube circuit. The tubes d6 and 48 are normally Vdirection to charge capacitor CV to volts.

non-conducting so that the tone signal appearing across T2 is not heard until the relay contacts 40 close. The momentary closure of contacts charges capacitor C12 positive to render control tubes 46 and 48 conductive. This attack rate is determined by the size of resistor Rd and capacitor C12. The decay or turn off time is determined by the size of capacitor C12 and resistor Re.

The switch 42 places resistor Rg in shunt with resistor Re to decrease the time constant of the discharge circuit for capacitor C12 and therefore decreases the decay time for tubes 46 and 48 and provides a variation in the percussion sound.

Normally, therefore, the 17,000 cycle tone present at transformer Tl is prevented from affecting relay 38 as the low pass filter 2S blocks the same from tube 30. When one of the keys, A1 for example, is operated, a portion of the 17,000 cycle tone is shunted through the key contact thereby changing the amplitude of the 17,000 cycle signal across transformer T1.

The initial change in amplitude of the 17,000 cycle signal gives rise to a positive going signal on the grid of tube 36 and the tube begins to conduct actuating relay 3S. The capacitor C11 determines the hold time of the relay and prevents chatter. n the meantime the tone signals are applied to transformer TZ over lead 13: and are initially sounded loudly with the momentary closure of contacts 40 and then immediately begin to sound less loudly at a rate determined by capacitor C12 and resistors Re and Rg until tubes 46 and 4S are completely cut olf.

If now the player operates a second switch, B1 for example, while maintaining switch A1 operating, the amplitude of the 17,000 cycle signal transmitted through transformer T1 changes by an additional increment and the process for introducing a percussion tone is repeated. This condition of course will occur on each key operation until the total number of operated keys is so great that a significant change in amplitude of the 17,000 cycle tone will not occur on operating an additional key.

Another arrangement for providing percussion control in response to signal changes in the 17,000 cycle signal appearing across transformer Tl is illustrated in FIG. 2. In FIG. 2, those portions which are similar to FIG. 1 are identically numbered for ease in comprehension with the major portion of circuit 10 being replaced by a block designated 10. In this case the grid of tube 36 is connected to capacitor C10 through a one megohm resistor RT and is connected to a source of -37 volt potential through a resistor R4. The plate is connected to a -5 volt potential and the cathode is connected to the -37 volt potential through resistor RV. A capacitor CV connects the cathode to ground. The -37 volt potential is also connected to the center tap on the secondary of transformer T2 through resistor RV and a resistor RZ and through the secondary to the grids of tubes 46 and 48. A capacitor CZ is provided in this connection. The cathodes of tubes 46 and 48 are connected to ground in place of +37 volts shown in FIG. 1.

With the just described connections, tone signals appearing on lead 13 are initially not heard because tubes 46 and 48 are cut off. The change in the amplitude of :the 17,000 cycle signal on operation of the keys is detected as before described to drive tube 36 into conduction. As this occurs, the cathode of tube 36 swings in a positive This potential appearing on the grids of tubes 46 and 48 turns them on. Since the pulse is of short duration, the tubes immediately move toward cutoff at a rate determined by capacitor CV and resistor RV. Resistor RZ and capacitor CZ determine the attack rate to complete the percussive envelope.

Thus, having described my invention, but believing it capable of numerous adaptations, there is appended hereto a series of. claims which are believed to describe the limitations of the invention.

I claim:

l. A legato percussion system for use in an organ having a plurality of keys each adapted to close a switch for rendering a tone generator effective to transmit a tone signal, the improvement comprising an impedance common to said keys, an impedance individual to each of said keys, means for connecting a signal to said common impedance, means for connecting said signal to either one or a plurality of said individual impedances responsive to the operation of a respective key whereby the signal level across said common impedance is altered in correspondence with the number of operated keys, and means for detecting each alteration of said signal for providing a percussive tone envelope to each transmitted tone signal.

2. A legato percussion system for use in an organ having a plurality of keys each adapted to close a switch for rendering a tone generator effective to transmit a tone signal, the improvement comprising a lead common to said keys and adapted to be connected to a respective impedance, another impedance connected to said lead, means for applying a signal between any of the respective impedanccs and said other impedance on operation of a respective key whereby the voltage drop of said signal across said other impedance is dependent on the number of operated keys to provide a voltage change on operation of each key irrespective of the continued operation of another key, and means associated with said other impedance for detecting each voltage change resulting from the operation of each key to permit the application of a percussion tone envelope to each generated tone signal.

3. A legato percussion system for use in an organ having a plurality of keys each adapted to close a switch for rendering a tone generator effective to transmit a tone signal, the improvementl comprising a lead common to said ke'fs and adapted to be connected to respective ones of said tone generators, a transformer primary connected to said lead, a high frequency signal source connected to said lead between said primary and said generators whereby the amplitude of the high frequency signal transmitted through said primary is dependent on the number of operated keys and is altered in response to the operation of each key irrespective of the continued operation of another key, means associated with said primary for detecting alterations in the amplitude of said high frequency signal resulting from operation of each key, means for applying a percussion tone envelope to each generated tone signal, and means for operating said percussion means responsive to each detected alteration in the amplitude of said high frequency signal.

4. A legato percussion system for use in an organ having a plurality of keys each adapted to close a switch for rendering a respective tone generator effective to transmit an audio signal to an output system, the improvement comprising a lead common to said switches and adapted to be connected to respective ones of said tone generators responsive to the operation of a respective key, a transformer primary connected to said lead, a high frequency signal connected to said lead between said primary and said generators whereby the amplitude of said high frequency signal transmitted through said primary is dependent on the number of operated keys, means associated With said primary for detecting only changes in the amplitude of said high frequency signal resulting from operation of each key, means for rejecting said high frequency signal from said output system, means for applying a percussion tone envelope to each generated tone signal, and means for operating said percussion means responsive only to detected changes in signal amplitude resulting from operation of said keys.

5. A legato percussion system for use in an organ having a plurality of keys each adapted to close a switch for rendering a respective tone generator effective to transmit a tone signal of corresponding frequency to an output system, the improvement comprising a lead common to said switches and adapted to be connected to respective ones of said tone generators, a transformer primary connected to said lead, a high frequency signal connected to said lead between said primary and said generators whereby the amplitude of said high frequency signal transmitted through said primary is dependent on the number of operated keys, means associated with said primary for detecting only changes in the amplitude of said high trequency signal resulting from operation of each key, means for applying a percussion tone envelope to each tone signal transmitted to said output system, means for detecting and amplifying said amplitude changes of said high frequency signal while rejecting both said high frequency signal and any tone signal, and means for operating said percussion means responsive only to said detected and amplitied amplitude changes in said high frequency signal resulting from operation of said keys.

6. The system claimed in claim 5 in which said means for operating said percussion means comprises a relay having a capacitor in shunt therewith.

7. The system claimed in claim 6 in which said means for operating said percussion means comprises a tube normally biased non-conductive.

8. The system claimed in claim 5 in which said percussion means comprises a pair o tubes arranged in a push pull circuit and to which said audio signals are applied for ampliication, an RC circuit connected to the grid of said tubes, and a normally non-conductive tube having an electrode connected to said RC circuit and arranged to be rendered conductive responsive to said amplied signal changes for charging said RC circuit to terminate the amplification of said signals by said pair of tubes.

9. A tone envelope control arrangement comprising a high frequency signal source, a plurality of tone signal sources, an impedance connected at one end to said high frequency signal source, means individual to each tone signal source for -connecting the respective source to the other end of said impedance whereby the amplitude of said high frequency signal appearing at the other end of said impedance is caused to vary in accordance with the number of tone signal sources connected to said impedance, means for transmitting only the tone signals connected to said impedance to an output system, and means operated only in response to the amplitude changes in said high frequency signal for applying a tone envelope to said transmitted tone signals.

l0. A signal amplitude sensing arrangement for operating a tone envelope control means comprising a high frequency signal source, a plurality of tone signal sources, an impedance connected at one end to said high frequency signal source, a common lead connected to the other end of said impedance, a switch individual to each tone signal source for connecting the respective source to said common lead whereby the amplitude of said high frequency signal appearing at said common lead is caused to vary in accordance with the number of tone signal sources connected to said impedance, means for transmitting only the tone signals from said common lead to an output system, and means operated only in response to a change in the amplitude of said high frequency signal on said common lead for operating a tone envelope control means.

ll. A tone envelope control arrangement comprising a high frequency signal source, a plurality of tone signal impedance sources, one impedance connected at one end to said high frequency signal source, a common lead connected to the other end of said impedance, another impedance connected to said common lead, a plurality of Contact sets individual to each tone signal source and adapted to be operated by a respective playing key for connecting the respective source impedance to said common lead, whereby the amplitude of said high frequency signal across said other impedance is caused to vary in accordance with the number of tone signal source impedances connected to said one impedance, means for transmitting only said tone signals on said common lead to an output system, and means operated only in response to a variation in the amplitude of said high frequency signal across said other impedance for applying a tone envelope to a tone signal.

References Cited in the tile of this patent UNITED STATES PATENTS 

1. A LEGATO PERCUSSION SYSTEM FOR USE IN AN ORGAN HAVING A PLURALITY OF KEYS EACH ADAPTED TO CLOSE A SWITCH FOR RENDERING A TONE GENERATOR EFFECTIVE TO TRANSMIT A TONE SIGNAL THE IMPROVEMENT COMPRISING AN IMPEDANCE COMMON TO SAID KEYS, AN IMPEDANCE INDIVIDUAL TO EACH OF SAID KEYS, MEANS FOR CONNECTING A SIGNAL TO SAID COMMON IMPEDANCE, MEANS FOR CONNECTING SAID SIGNAL TO EITHER ONE OR A PLURALITY OF SAID INDIVIDUAL IMPEDANCES RESPONSIVE TO THE OPERATION OF A RESPECTIVE KEY WHEREBY THE SIGNAL LEVEL ACROSS SAID COMMON IMPEDANCE IS ALTERED IN CORRESPONDENCE WITH THE NUMBER OF OPERATED KEYS, AND MEANS FOR DETECTING EACH ALTERATION OF SAID SIGNAL FOR 